Add progressive web app companion for cross-platform access

Vite + TypeScript PWA that mirrors the Android app's core features:
- Pre-processed shelter data (build-time UTM33N→WGS84 conversion)
- Leaflet map with shelter markers, user location, and offline tiles
- Canvas compass arrow (ported from DirectionArrowView.kt)
- IndexedDB shelter cache with 7-day staleness check
- Service worker with CacheFirst tiles and precached app shell
- i18n for en, nb, nn (ported from Android strings.xml)
- iOS/Android compass handling with low-pass filter
- Respects user map interaction (no auto-snap on pan/zoom)
- Build revision cache-breaker for reliable SW updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pwa/node_modules/es-abstract/2021/QuoteJSONString.js

@@ -0,0 +1,52 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var callBound = require('call-bound');
+var forEach = require('../helpers/forEach');
+var isLeadingSurrogate = require('../helpers/isLeadingSurrogate');
+var isTrailingSurrogate = require('../helpers/isTrailingSurrogate');
+
+var $charCodeAt = callBound('String.prototype.charCodeAt');
+var $strSplit = callBound('String.prototype.split');
+
+var StringToCodePoints = require('./StringToCodePoints');
+var UnicodeEscape = require('./UnicodeEscape');
+var UTF16EncodeCodePoint = require('./UTF16EncodeCodePoint');
+
+var hasOwn = require('hasown');
+
+// https://262.ecma-international.org/12.0/#sec-quotejsonstring
+
+var escapes = {
+	'\u0008': '\\b',
+	'\u0009': '\\t',
+	'\u000A': '\\n',
+	'\u000C': '\\f',
+	'\u000D': '\\r',
+	'\u0022': '\\"',
+	'\u005c': '\\\\'
+};
+
+module.exports = function QuoteJSONString(value) {
+	if (typeof value !== 'string') {
+		throw new $TypeError('Assertion failed: `value` must be a String');
+	}
+	var product = '"';
+	if (value) {
+		forEach($strSplit(StringToCodePoints(value), ''), function (C) {
+			if (hasOwn(escapes, C)) {
+				product += escapes[C];
+			} else {
+				var cCharCode = $charCodeAt(C, 0);
+				if (cCharCode < 0x20 || isLeadingSurrogate(cCharCode) || isTrailingSurrogate(cCharCode)) {
+					product += UnicodeEscape(C);
+				} else {
+					product += UTF16EncodeCodePoint(cCharCode);
+				}
+			}
+		});
+	}
+	product += '"';
+	return product;
+};